The AMC Jeep 4 liter I-6 is indeed legendary. This one has even survived 2 overheats, sludge and a cylinder head replacement. All 6 plugs were in this condition and the vehicle has 150k on the odometer.

The co-worker who owns this particular 2001 Jeep Grand Cherokee (of which these plugs are from) said yesterday it finally started to hesitate and stumble. LOL

A nickel for rough comparison...